Results 1 to 12 of 12
  1. #1
    mtbr member
    Reputation: eurospek's Avatar
    Join Date
    Sep 2007
    Posts
    5,374

    Looking to upgrade Shimano SLX M665 brakes to XT M785 or Saint M810?

    I currently have Shimano SLX M665 brakes, 203/180 rotors RT75 rotors and resin pads (tried out recently metal pads but didn't care for the on/off feeling, lost some modulation).

    I've been thinking of upgrading the brakes to something stronger, but I don't want to give up modulation, I don't have a lot of DH sections, but sometimes I feel the SLX are overpowered by the trail, heat up, fade a bit, and squeal coming down.

    I can buy Saint M810 used for $275 (going price on ebay or PB), reuse my current rotors and probably switch out the metal pads for resin. But the more I've been reading about them, people say they lack modulation and have that on/off feeling. I'm 6'4" 230 lbs but I'm thinking going with the Saints might be overkill for trails around Wisconsin.

    Which leads me the the 2012 XT M785 brakes and Ice Tec rotors. I would go 203/180 again but get new Ice Tec rotors to take advantage of the technology and the reviews have been great thus far for them, apart from a few leaking units lol. Also noticed that these ship stock with metal pads which I would probably keep for the time being and get used to them.

    Price wise, I can get brand new XT M785 brakes, Ice Tec rotors, and a warranty for a little more than the Saints.

    What' a guy to do wanting stronger brakes with lots of modulation? TIA!

  2. #2
    mtbr member
    Reputation:
    Join Date
    May 2011
    Posts
    81
    That's a no-brainer, go for the XTs. Apart from resistance to overheating (partly due to heavier caliper), the XTs outperform the Saints in almost every aspect.
    Last edited by anlin; 08-19-2012 at 02:25 AM.

  3. #3
    mtbr member
    Reputation: eurospek's Avatar
    Join Date
    Sep 2007
    Posts
    5,374
    Quote Originally Posted by anlin View Post
    That's a no-brainer, go for the XT's. Apart from resistance to overheating (partly due to heavier caliper), the XT's outperform the Saints in almost every aspect.
    Even with a 2 piston difference? Looking more and more, I think I'm headed that way too, just need to find a set with rotors under $300.

  4. #4
    mtbr member
    Reputation:
    Join Date
    May 2011
    Posts
    81
    Quote Originally Posted by eurospek View Post
    Even with a 2 piston difference?
    Yes! Given the same master cylinder, the caliper with the most combined piston surface area will produce the most clamping power.

    Combined piston S.A. of Saint calipers (2x16mm and 2x14mm pistons IIRC):
    2 * ((16/2)˛ * PI) + 2 * ((14/2)˛ *PI) = ~710mm˛

    Combined piston S.A. of XT M785 calipers (2x22mm):
    2 * ((22/2)˛ * PI) = ~760mm˛


    The XT caliper has more piston surface area than the Saints, which given the same master cylinder piston surface area (which to my understanding is constant across the whole Shimano line) means that the XTs will have a higher mechanical/hydraulic advantage, producing more clamping power for given lever pull force.
    Furthermore, as friction is the product of the CoF of brake pad against steel and the normal force applied to the brake pad (notice how pad surface area is not in the equation!), the larger pads in the Saints shouldn't add to the power at all. The larger pads do, however, have some advantages for extreme DH use, like wear resistance and possibly some benefits in heat management.

    Quote Originally Posted by eurospek View Post
    Looking more and more, I think I'm headed that way too, just need to find a set with rotors under $300.
    Shouldn't be too hard, there have been many great deals on these brakes lately.
    Last edited by anlin; 08-19-2012 at 02:34 AM. Reason: grammar and additional info

  5. #5
    mtbr member
    Reputation: eurospek's Avatar
    Join Date
    Sep 2007
    Posts
    5,374
    ^ That's awesome, didn't even bother to think about it that way, figured 2 more pistons, better braking power. Your calculations have definitely sealed the deal.

    Question now, is do I stick with 203/180 rotors or maybe even downsize to 180/160? And I wonder why these are shipping stock with metal pads instead of resin.

  6. #6
    mtbr member
    Reputation:
    Join Date
    May 2011
    Posts
    81
    Quote Originally Posted by eurospek View Post
    ^ That's awesome, didn't even bother to think about it that way, figured 2 more pistons, better braking power. Your calculations have definitely sealed the deal.

    Question now, is do I stick with 203/180 rotors or maybe even downsize to 180/160? And I wonder why these are shipping stock with metal pads instead of resin.
    I forgot to mention in my previous post that the calculations are purely theoretical and do not necessarily reflect actual performance, although in this case I have found theory and real world performance to stack up really nicely, as the XTs really do feel at least as powerful as the saints.

    As for rotor size, the 180's will definitely be more than powerful enough, whether they can handle the heat depends on your riding style. I am close to your height, only a little lighter and the power of the 2012 SLX's (equivalent to XT, only less adjustments) I have on my hardtail is downright scary, even with 180mm rotors. In fact, the first time I tried these brakes I managed to pull off a one-finger OTB on flat ground. They are that powerful. It takes a few rides to get used to the power even though these are fantastically controlled brakes.

    Regarding pad compounds, I'm not sure why Shimano went with sintered instead of organics on these, but luckily the pads are easy enough to swap out.

  7. #7
    mtbr member
    Reputation: Slurry's Avatar
    Join Date
    Dec 2008
    Posts
    607
    quad-piston brakes are for supporting a much bigger brake pad.

    I noticed a huge bump in power and performance going from M665 to M666 brakes (203/180 rotors on a 29er, both brakes had sintered pads)

  8. #8
    mtbr member
    Reputation: eurospek's Avatar
    Join Date
    Sep 2007
    Posts
    5,374
    Quote Originally Posted by Slurry View Post
    quad-piston brakes are for supporting a much bigger brake pad.

    I noticed a huge bump in power and performance going from M665 to M666 brakes (203/180 rotors on a 29er, both brakes had sintered pads)
    I just can't decide what rotor size I should get. With the Ice Tech rotor pricing, I want to get it right on the first try lol.

  9. #9
    mtbr member
    Reputation:
    Join Date
    May 2011
    Posts
    81
    Quote Originally Posted by eurospek View Post
    I just can't decide what rotor size I should get. With the Ice Tech rotor pricing, I want to get it right on the first try lol.
    I feel your pain! I too recently ordered a new set of discs. Took me almost a week to decide which sizes to get!

    I really don't think you will need anything larger than 180mm front or rear. If anything, I think a larger rotor might even be too grabby for your purposes. I currently have a weird 170mm disc I found up front and can overpower the front tyre in pretty much any terrain except for dry asphalt with just one finger on the lever.

  10. #10
    mtbr member
    Reputation:
    Join Date
    Mar 2008
    Posts
    9
    I agree with the theoretical calcs of the earlier poster, but I will give my personal experience of the following 3 shimanos:

    LX Deore m585
    XTR trail 988
    Saint 810

    The 3 most important things on a bike for me are tires, fork and brakes. To me they all have their importance at some point during the ride. That said, I started back into biking with some hayes hfx 9 carbon brakes, with poor power, but good feel. My next bike had Juicy carbon with great power and the worst feel ever. The next was a DH bike with LX brakes. I know, underpowered for a DH, but great feel. After having these shimano, even on a DH, I will never buy any brake but a shimano!!! I traded the LX for a Saint and holy $hit! The power on these is so strong, if you don't ride them a LOT and have good brake feel you will lock up both tires way more than you prefer!!! I have ridden codes, elixer, formula the one, and all can feel ok, but I thought the saint was 50% more power than the next closest.

    To rate these brakes for power with saint being the most at 100%, I would put the XTR trail at 85% and the lx around 40%. The modulation for each is comparable to the power, so as the power goes up, the modulation goes down and you have to be carefull not to skid both tires. I prefer the modulation via finger power vs having to hammer a lever after 10 minutes of DH to get enough power to stop.

    My recommendation is the LX for your gf. (mine is 115) They stop her well, but won't make her crash, blame me and leave my a$$. The XTR trail for anything up to AM / lite FR. Saint for DH only. I want as much power as I can manage for each bike, but I just don't think I could ever manage Saints on an AM. I read a while back that Mark Weir had Saints on his Nomad with small rotors and recently switched to XTR trail with a bigger rotor. I have the same XTR with a 203 up front (only size for fox 180 fork) and 160 rear. I would put a smaller up front if I could cause i'm no Weir!!!

    Again I agree in theory with the previous poster about hydraulic leverage, but in practice, the Saint is a moto brake!

  11. #11
    mtbr member
    Reputation:
    Join Date
    May 2011
    Posts
    81
    Quote Originally Posted by inoack View Post
    I agree with the theoretical calcs of the earlier poster, but I will give my personal experience of the following 3 shimanos:

    LX Deore m585
    XTR trail 988
    Saint 810

    The 3 most important things on a bike for me are tires, fork and brakes. To me they all have their importance at some point during the ride. That said, I started back into biking with some hayes hfx 9 carbon brakes, with poor power, but good feel. My next bike had Juicy carbon with great power and the worst feel ever. The next was a DH bike with LX brakes. I know, underpowered for a DH, but great feel. After having these shimano, even on a DH, I will never buy any brake but a shimano!!! I traded the LX for a Saint and holy $hit! The power on these is so strong, if you don't ride them a LOT and have good brake feel you will lock up both tires way more than you prefer!!! I have ridden codes, elixer, formula the one, and all can feel ok, but I thought the saint was 50% more power than the next closest.

    To rate these brakes for power with saint being the most at 100%, I would put the XTR trail at 85% and the lx around 40%. The modulation for each is comparable to the power, so as the power goes up, the modulation goes down and you have to be carefull not to skid both tires. I prefer the modulation via finger power vs having to hammer a lever after 10 minutes of DH to get enough power to stop.

    My recommendation is the LX for your gf. (mine is 115) They stop her well, but won't make her crash, blame me and leave my a$$. The XTR trail for anything up to AM / lite FR. Saint for DH only. I want as much power as I can manage for each bike, but I just don't think I could ever manage Saints on an AM. I read a while back that Mark Weir had Saints on his Nomad with small rotors and recently switched to XTR trail with a bigger rotor. I have the same XTR with a 203 up front (only size for fox 180 fork) and 160 rear. I would put a smaller up front if I could cause i'm no Weir!!!

    Again I agree in theory with the previous poster about hydraulic leverage, but in practice, the Saint is a moto brake!
    Could the switch to larger rotors have something to do with the lever geometry between the brakes? The long lever and low pivot point of the Saint lever (due to radial MC) means the brake is best suited for 2 or 3 fingers on the lever. The XTR levers are extremely short in comparison and the pivot point has been moved much closer to the bar, making the XTRs much better suited for 1 finger braking.

    I have tried the Saints, and my subjective opinion is that the 2012-2013 brakes are still stronger. Stoppies with one finger on the lever were possible but required a lot of effort with the Saints, whereas with my SLXs I can do the same with ease.

  12. #12
    mtbr member
    Reputation:
    Join Date
    Mar 2008
    Posts
    9
    Quote Originally Posted by anlin View Post
    Could the switch to larger rotors have something to do with the lever geometry between the brakes? The long lever and low pivot point of the Saint lever (due to radial MC) means the brake is best suited for 2 or 3 fingers on the lever. The XTR levers are extremely short in comparison and the pivot point has been moved much closer to the bar, making the XTRs much better suited for 1 finger braking.

    I have tried the Saints, and my subjective opinion is that the 2012-2013 brakes are still stronger. Stoppies with one finger on the lever were possible but required a lot of effort with the Saints, whereas with my SLXs I can do the same with ease.
    In retrospect, I wasn't that clear, but I have my brakes set to one finger brake only. I love the brake levers that have room for 3 fingers!!!! who can hang on to a handlebar with a thumb and a pinky!?!? lol. Possibly better leverage between models, dunno. I haven't played around with different rotor size too much, but again, theoretically, a larger rotor should give better leverage and braking power.

    After thinking about a stoppie, it's easiest on my xc bikes and hardest on my DH. I always attributed this to the geometry. I sit much higher and more forward with a steeper head angle on my XC, but the DH is opposite, lower, farther aft, and super slack head angle. My experience in general is there are good brands and bad brands. After that the differences are more subtle and come down to specific rider preference and tuning!!! My overall experience with avid bb5, juicy carbon, juicy 5, 7 is good power, bad vibration. Hayes hfx9, stroker trail, stroker ace bad power, good feel. Shimano is great power great feel. I have friends with magura and formula with great results as well, but I like equiptment that I can find parts to easily.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •